The reinforced plastic industry has been using glass fibers in various forms for reinforcing polymeric matrices to produce a wide variety of products. The glass fibers have been used in the form of continuous and chopped filaments, or strands, mats, rovings and various woven and nonwoven fabrics.
In producing glass fibers, for use as polymeric reinforcements, the glass fibers are attenuated from molten streams of fiberizable glass material flowing from a bushing which is connected to a furnace containing a pool of molten fiberizable glass. The glass fibers are typically attenuated by a winder which collects gathered filaments into a package or by rollers which pull the fibers before they are collected and chopped. In the process of producing glass fibers, a chemical treating composition is applied to the fibers shortly after they are attenuated from the molten stream of glass which emanates from the bushing.
The chemical treating composition is an aqueous composition, typically containing a film former system, coupling agents, lubricants, emulsifiers or surfactants and anti-static agents. The chemical treating composition, or size, is needed to retard interfilament abrasion of the glass fibers when they are gathered into a bundle or strand. In this way the high strength of the glass is helped to be maintained. The treating composition also makes the glass fibers compatible with polymeric matrices which they are ultimately intended to reinforce. In this respect the best results are attained when the film former is partially soluble in the pre-cured and predried version of the matrix polymer which the sized fiber is ultimately intended to reinforce. After the fiber is treated with the aqueous size formulation, the fibers typically are dried in the package form or in a chopped strand form before they are used for reinforcing polymeric matrices.
Clear or translucent plastic panels reinforced with glass fibers find application in solar collectors, skylights, patio covers, highway signs and markings and greenhouse glazings. Such panels are continuously produced by chopping glass rovings and forming a blanket of such chopped rovings on a plastic sheet, for example, Mylar material, while the sheet is moved on a conveyor. The rovings are then treated with a matrix resin, or binder, typically in the form of a solution of a thermosettable uncured polyester resin in styrene monomer. The resin impregnated roving blanket or mat is then coated with another sheet, for example, a Mylar sheet, and cured. The thickness of these panels is generally on the order of two or three millimeters to ten millimeters or more.
The sizes employed for coating fibers intended for use in producing plastic panels have certain unique demands upon them which are in addition to the general nearly universal requirements of a size. One additional requirement is that the sized glass fibers not reduce the weatherability of the panels and that high weather resistance be maintained for extremely long periods of time. Another requirement for such a size is that it must not allow the fibers to reduce the clarity of the panels with time. For example, if the size is not proper there is a tendency of the fibers to become very prominent, that is turn the panel white instead of maintaining the clear or transparent quality of the panels. Such whitening, of course, makes the panels unsuitable for their intended purpose as such as solar collectors, skylights, greenhouse glazings and the like. Another characteristic, of course, is that the sizes must render the fibers processable in the production of the panels. The size must not be so soft and tacky that the fibers will stick to each other upon being chopped; that is they must air disperse readily. Furthermore, the size on the glass fibers must have good wet out with the applied matrix resin; that is, the sized fibers must disperse readily in the polymeric resin matrix solution.
While many sizes have been employed there is nonetheless, a need in the art to provide improvements in the sizes so fibers will have qualities discussed above.
In accordance with the present invention glass fibers are provided with an improved size, the fibers thereby being well adapted for use in reinforcing numerous products, but especially being well adapted for forming panels. These fibers with their new size provide panels which have outstanding long term weatherability and clarity. The sizes likewise provide the fibers with a highly desirable attribute of dispersibility, both with regard to the chopping process and with regard to solution, or solvation, in the matrix resin.